Abstract: The ceramides according to the invention are compounds corresponding to the formula: ##STR1## in which: R.sub.1 is a C.sub.11 to C.sub.21 alkyl or alkenyl radical; R.sub.2 is a linear or branched C.sub.1 to C.sub.29 hydroxyalkyl radical or a C.sub.7 to C.sub.29 hydroxyaralkyl radical, these compounds being in the form of a racemic mixture of the erythro and threo diastereoisomers for the aminodiol part ##STR2## in erythro:threo ratios of from 85:15 to 20:80. Application to cosmetic and dermopharmaceutical compositions.

Abstract: A method for preparing carboxylic acids including (n+1) carbon atoms, or the related esters, by liquid phase carbonylation of an alcohol including (n) carbon atoms, in the presence of a uniform catalytic system based on at least one iridium compound and at least one halogenated promoter. In particular, the method is characterised in that the content of ester related to said carboxylic acid and alcohol is kept between 15 and 35% in the medium during the reaction, while the halogenated promoter content is kept between 10 and 20%, and the partial carbon monoxide pressure is 40-200 bar. Said method enables both the rate of carbonylation and the acetic acid selectivity to be increased.